The Principle and Application of a Novel Rotary Percussion Drilling Tool Drived by Positive Displacement Motor

Abstract

Abstract Experience over the past decades has proved that rotary percussion drilling technology is one of the most effective ways in improving the rate of penetration in deep wells. In the rock breaking process, the drill bit's teeth are forced into the rock powered by the bit weight and impact load, then the contact surfaces of rock and PDC teeth are destructed gradually. The finite element software was used to simulate the process of one PDC tooth breaking up the sandstone with the rotary percussion technology. The force on one PDC tooth in rotary percussion drilling was constantly fluctuating, and the impact load added the instability of load curve. The maximum mechanical strain appeared at the fracture surface, but not the contact surface of the rock with the PDC tooth. When the rock broken reached a steady state, the ratio of eroding energy to total energy consumption stabilized at around 52%. The research showed that rotary percussion drilling technology is still not mature in the aspects of high-efficiency, long-life, and low-cost. The improvement of the comprehensive performance of the percussion tools needs more intensive study. This paper's objective is to design a novel rotary percussion tool to generate impact load. This new tool uses a positive displacement motor that drives the hammer piston to rotate, meanwhile the piston hits the anvil to generate impulse pulse. Also this tool's impact properties were tested and analyzed through field experiments. The impact frequency of this novel tool is 25.7~37.2Hz, which is adjusted by the flow rate of drilling fluid. The peak value of impact load is 20~42kN, adjusted by spring's compression. Drilling tests in laboratory experiments showed that the rotary percussion drilling can significantly increase the rate of rock broken, and the highest rate of speed-up compared with the common drilling is 64.2%. Increasing spring compression can improve the rate of penetration in these percussion drilling experiments. A good performance in drilling sandstone experiments in lab experiments proves that this novel tool is helpful in improving the ROP in drilling deep wells onshore and offshore.